Heat exchanger



Feb. 9, y1960 J. D. wlLKlNs Y 2,924,437

HEAT EXCHANGER Filed March 2l, 1955 2 Sheets-Sheet 1 gli J. D. WILKINSHEAT EXCHANGER Feb. 9, 1960 2 Sheets-Sheet 2 Filed March 21, 1955 UnitedStates Patent O HEAT EXCHANGER John D. Wilkins, St. Louis, Mo., assignorto Olin Mathieson Chemical Corporation, East Alton, Ill., a corporationof Virginia Application March 21, 1955, Serial No. 495,542.

1 Claim. (Cl. 257-130) second o r outlet header. The conduits or tubesserve to carry within themA a confined heat exchange medium such4 aswater, steam, or` the like, in conductive relationship'with anothermedium such as air or other gas passing between the tubes. fabricatedfrom sheet metal is typical of automobile radiators, for example, wherethe heated water, issuing from the cooling block of the engine with theaid of a pump, first enters one of two headers, passes through a greatnumber of thin walled relatively flat closely Vspaced tubes, betweenwhich cooling air is blown and which extend usually vertically from oneto the other of the headers, and then, after undergoing cooling in thetubes, is collected in the second header from whence the coolant isreturned to the engine block and the pump.

` As manufactured presently, this type of heat exchange unit is ratherexpensive inasmuch as the methods which heretofore achieved anycommercial importance usually `involved a great multiplicity of brazingor soldering operations, and also involved handling and aligning ofnumerous parts and'joining them together. lt will be appreciated thatsuch radiator constructions are not entirely suited for mass productionmethods, and consequently are quite costly. In radiators of suchconstruction, it is not uncommon for a considerable number of the tubesto have leaks at the joints immediately after fabrication, whichrequires extensive inspection and testing facilities, together withrepair facilities, all of which add to the cost of manufacture.Moreover, during service ysuch units tend todevelop leaks `at the jointsall too soon, and then usually require such intricate and expensiverepairing as to make costly replacement of `the entire unit often moreeconomical than repair of the joints. Furthermore, the heat exchangeunits of this type are usually assembled with sheet metal fin stock ofone type or another of relatively thin gage as compared to the gage ofthe tube walls. A well-known type of yfin stock consists of thin metalstock such as copper alloy having a thickness of about 0.003 of an inch.Assembly of the tubes and the fins itself involves a rather complicated,additional procedure of stacking a considerable number of separate tubeswith a considerable number of separate strips of fin stock. As a result,,the core section of heretofore known radiator constructions of thistype constitutes the part of the radiator most dilicult to manufacture,and the part responsible for the high cost of the completed heatexchange unit.

A principal object of the invention is to provide a novel and improvedheat exchange core unit free from the aforementioned disadvantages vofconstruction, and a This type of construction new and improved method ofconstructing the same. A further object of this yinvention is to providea heat exchange unit core structure in which a great multiplicity offluid conduits are integrated into a single structural member, and henceis admirably suited to mass production methods.

Another object of the invention is theprovision of a heat exchanger corestructure having closely spaced sheet metal elements integral with eachother, and so formed as to improve the rigidity of the core and toeliminate a considerable number of seams and separate tins. Otherobjects and advantages will be apparent and the invention will be betterunderstood, from the following description when read with reference tothe accompanying drawings, in which:

Figure l is a perspective view of a typical automobile radiator having acore constructed `in accordance with the present invention, part beingbroken away to reveal the internal relationship of the integral parts;

Figure 2 is a view in front elevation of a section of the radiator shownin Figure 1;

Figure 3 is a sectional view taken along line 3--3 of Figure 2;

Figure 4 is a sectional view taken along line 4-4 of Figure 2;

Figure 5 is a plan view of a flat unified sheet structure of which thecore shown in Figures 1 4 is made, the upper half of the thickness ofsaid unified sheet structure being in part torn away to reveal thelocation of bonded and unbonded areas between the upper and lower halves(thickness wise) of the unied sheet; and

Figure 6 is a sectional view at greatly enlarged scale taken along line6 6 of Figure 5. i

Therpresent invention contemplates the manufacture of a self-sustainingcore member containing a great multiplicity of integral, butindividually distinct, liquid conduits of small cross-section from apair of flat sheets which, with intervening stop-weld material in apattern of parallel spaced strips, have been unified by pressure andthen distended, as vtaught in United States Patent No. 2,690,002 to L.H. Grenell; and zig-zag folding the unified sheets so as to provide analigned series of laps or conduit panels (each containing one or moreconduits) with each panel integrally connected to its neighbors oneither side thereof. The invention contemplates that the pattern ofstop-weld material be so coordinated with the pressure unifyingoperation, and with the folding to be done, that an air circulationspace can be provided on both sides of each conduit panel withoutservering the integral connection between panels.

More specifically, the invention contemplates that the stop-weldmaterial, which determines the location and magnitude of' the fluidconduits, be laid out in a pattern such that the flat unified sheet canbe folded at the desired lines after distention of the fluid conduitpattern without interrupting the continuity of the passageway throughthe conduits, or distended after folding without danger that somepassageway, or some part thereof, will not distend because of thestresses due to a fold close-by. In the embodiment to be described indetail, the pattern of stopweld material is such that the Welded areabetween the conduits, or cavitated portions in a given panel isminimized in the interest of providing the greater number of conduits inthe panel or laps, but between the endmost conduits of adjacent panelsor laps, a welded web of greater extent is provided whereat the fold maybe made, but it will be understood that the welded web between lallconduits may be made wide enough to permit the folds to be made at anyof them, or that the fold may be made part in the web on one side, andpart in the web on the other side of a given conduit without interferingwith the continuity of passage through the conduits.

In order to provide for the circulation of air between, and transverseto, the' direction ofthe conduit panels, perforations may be providedintermediate the conduits, or cavitated portions, perrni ing the passageof air between the panels or laps. ex mpleas illustrated in thesucceedinlg example the connec mg web, at the frontand rear, betweenpanels may be cut away to a large extent; and if the metal cut out beleft integral at one edge to formv ears of metal cut out of the panelsadapted to contact the exterior ofthe tube walls of adjacent panels,forexample, it may be bent in between the panels to actas a spacer andair baffle.

The pattern of stop-weld material contemplated by the present inventionis such that the pressure unification and subsequent distendingtechnique, taughtfby the aforesaid Grenell patent, can be utilizedpractically Without limitation as to size of the integral core beingproduced. Where the component sheets are to be pressure unified byrolling, as is usual, and the rolling is in the direction of the lengthof vthe stop-weld strips which denethe respective conduits, the Ysize ofthe integral core to be produced is limited only by the width of therolling mill. On the other hand, where the component sheets rare rolledin the direction transverse to the length of said stop-weld strips, themagnitude of the integral core to be produced is limited only by thelength of the facilities for handling astrip as it is fed into andemerges from the rolling mill.

The pressure unification of the initially separated .sheets (with thepattern of stop-weld material intervening) by rolling to a reduction ofat least 35% in thickness, with corresponding elongation, producesasingle phase weld between the component sheets (at all areas thereofnot protected by stop-weld material) without reducing the metal toafluid body, and consequently ,the physical .characteristics and microstructure of the unified sheet are uniform throughout its thickness andarea, as all components thereof have received the same degree ofmechanical work and have been subjected to the same degreeof heattreatment. Upon the completion of such Va pressuregunitication, nointerface between the initial component `strips is discernible, andconsequently, the resultant sheet may be manipulated in the sarne manneras a single sheet initially rolled to the same thickness. Copper alloys,aluminum alloys, and steel respond readily to pressure unification abouta pattern of stop-weld material as `above described. The initial sheetsmay, for example, be of an alloy composed of 92 to 94% copper, 2.05% toy2.60% iron, phosphorous in an amount up to 0.025%, lead in an amount upto 0.05 %1, and the balance zinc. Such sheets may initially have athickness on the order of 0.070 inch so` that, after -the usualdegreasing and cleaning operations, the chosen pattern of stop-weldmaterial (which may con- .sist of a mixture of graphite in water-glass)is applied to one such sheet; and another such sheet then superimposedupon the first sheet so as `to produce a pile having a thickness on theorder of 0.140 inch. This pile is then subjected to hot rolling toreduce the thickness of the pile, unify the component sheets, vandelongate the same. In any such operation, it will be understood that thepattern of stop-weld material elongates to the same extent that themetal elongates, and consequently, allowance must be made for suchelongation in the direction of rolling, as the unwelded area, dened by astrip of stop-weld material one unit long (in the direction of rolling)will have grown inlength as an incident to the rolling operation.

'The accompanying drawings illustrate an embodiment of the invention asexemplified by the core for an automobile radiator. The core, with thegreat multiplicity of tubes therein, is an integral structure producedfrom a at plate resulting from the pressure unification of two sheets ofmetal (with intervening pattern of stop-weld material) as abovedescribed, and which,after being subjected tothe necessary reductionandelongation in a roll- ;ing mill, v,is Vshown in Figure 15 -AsindicatedinFigure 5,

a single suchrnnitied;sheetmayprovide.thestockzforthe 4 manufacture of aplurality of cores, and the sheet may be cut up into sections''such"'as'the' section embraced between the lines A-A and B-B, toprovide the stock for a single integral core. The particular sheet shownin Figure 5 has been pressure unified by rolling in the directionindicated by the arrow at the left of the figure. Prior to rolling,there were two component sheets, 1 and 2. On the former, a pattern lofstopfweld `material was applied such that, after the elongation thereofin rolling, the pattern shown by the stippled section of Figure 5resulted. In the embodiment shown, the stop-weld material defines aseries of three longitudinally extending'strips 13v Iseparated byintervening strips 4, which are unprotected bythe stopweld material. Thethree strips 3,A with intervening strips 4, are repeated a numberoftimestransversely of the sheet 1, and each repetition thereof isseparated by an unprotected strip 5 of greater width than theunprotected strips 4. Along the outer margins of the sheet, there is anunprotected strip 6, andbetweenthepattmfor successive cores', there isan unprotected s'tripflj ,EXtending transversely of the sheet, andlc,"neetirgfoneendfof all stopweld ,strips 3, there is asti-ip ofstopweldmaterial which eitends'to `one marginof thesheet'. During lthe'.rolling operation, the two `sheets V1 and'ZfbeC/Qre Pressure unified mano f .the areas unprotected-breton-weld material, ,to wit: 4,' 5,;,61,and 7, while at theareafsSandpwhich lare protected by stop-weldVrrrateriral,- vthere is no `rvvelding or unification between I thesheetsland 2L 'i Given the' potiorif .ther ,ifled 11er` .sheet @dined b etweenlines A--A andBA-FB oflFig'ure 5 "the location of the terminus oflstop-weld strip y,thy argin` .ofthe sheet-is ascertained, andan,inflation tool ainserted thereat. By theintroduction of fluid underiplressurefthe portions of sheets ,1 `and. A2, which'overlie andunderliethe lstrips ofs't'oPWeld material ,3 and 8,`are v`cllistendedinto tubes. The distended structure `isfthen cut volf along lines X-Xand L-Y,` Either before for after `such distentiongwliile still in `theflat, suchop'enings asfrn'ay be'des'ired 'are punched, sheared, orextruded lin jareas :Sbetween fthe rightrnost stripV 3 -of one series,andtheleftmo'st istrip 3 of the ,IICXt Sries. 'if beinaundrtg0d-thf,theldgss ',Of Such Openings .are 4adequately .spaced ,from th ad'ieritStrips 3 ytof.rriaiiltain .a secure weld bei een sheets .1 .and l2 it'the sides'of's'uch strips 3. 'Y A` The Vsheet. maythenbe Ligfzagfolded, as xshown in Figures 3 and 4, to Iprovide`,an`` aligned lseries'of tube panels 9, 10,-11and 12untiltyl-1e` entire width offthe sheet ofstock shown in' Figure v,5 .is folded. 11n yotherwords, the metal whichsurrounds ,the tubes result Ifrom inflation Vof each series .ofthreestrips 3 cfons'titntes a single panel, s uch as V9, 10, 11, `or`12', and ltlereare Aas many such panels in theQzigzagfolded ystructures,there -are series ofthree strips 3 in the llat'sheetshownin ,Figure'Upon inflation of the unified Lslieet," atubfe 13As prosuceda each ofthe@endangered by he strips of stepweld `materialpand between such tubes'`llnluat the unprotected areas .4," ther`e is produced i t` rovnn'ectingweb 1,4. Likewise, at the unprotected are K5 (between the .outmost`strips `3 o-fleach series), there `:is vproduced a wider web gln the,Zig- ;agfolding, ofthe sheet into the yseriesbl aligned panelsjust4described;the 'fold is ymade at webs 1 5, which .are vof 4widthsuiiicientfnot'o'nly to accommodate the foldv without collapsing`,the.\adjac ent tubesgbnt also suicientto provide anaireirculation'space between each tube'.pane'lfa'ndv its neighbors.

As previously mentioned, the webs 1'5 may .be perforated orotherwiselargelyzcut away. In the embodiment shown in the drawings,aseries of openings' 16 is yprovided in each ofthefwebs 15 .both :atkthefrontand atthe may be of such longitudinal extent as to provide almostcomplete ventilation height-wise of the core, said openings beingseparated only by relatively narrow bridge piece 18 of dimensionssufficient only to retain the several tube panels 9, 10, 11, 12, andothers like them, in integral connection and in proper alignment. As theprincipal direction of air travel through the core is transverse to thelength of tubes 13 (as indicated by the arrow in Figure 3), therelatively large openings '16 in webs 1-5, at the front and rear of thezig-zag folded structure, provide for the ingress and egress of air intoand from the space between successive tube panels '9, 10, etc. Aspreviously stated, the edges of the openings 16 must be spaced from thetubes 13 to leave sufficient residual metal in web 15 that a secure Weldis maintained between sheets 1 and 2 at the sides of the tubes (or atthe sides of the strips '3, if the holes 1-6 be formed before the tubesare distended). This residual part of web 1S, when bent as shown inFigures 3 and 4, adds stiffness to the panels adjacent the openings 16at both the leading and trailing edges thereof.

For the sake of clarity in the drawings, the space between adjacentpanels 9, 10, etc., as well as the size of the tubes 13, is shown largerthan need be in practice. In fact, in actual practice, it is preferredthat each tube panel have as many tubes as can be accommodated withinthe dimensional 4limits of the panel. Of course, the greater theexternal area of the panel in proportion to the volumetric content ofthe tubes, the more e'icient will be the heat dissipation, as not onlythe portion of the panel which forms the exterior walls of the tubes,but also the portion thereof which forms the intervening webs 14, andthe webs 15 serve as fins to dissipate heat from the water passingthrough tubes 13.

The core as thus constructed is appropriately mounted between top andbottom headers 20 of any suitable construction with a fluid-tightconnection t the several tubes 13, and is confined sidewise withinappropriate members 21. As previously pointed out in connection withFigure 5, the completed core does not include the area of the pressureunitied plate which is delineated by the transverse strip 8 of stop-weldmaterial. The strip 8 serves only to delineate a channel through whichall of the unwelded areas 3/ may be simultaneously inflated anddistended; and consequently, where it is more economical to individuallyinate the several areas 3 than to waste the metal which is involved inproviding such a cross channel, the strip 8 may be eliminated and themetal overlying and underlying the same conserved. Such would be thecase in situations where it is desired to assemble the core withinheaders 20 before the unwelded areas are distended into tubes.

From the foregoing description, those skilled in the art should readilyunderstand the construction and operation of the radiator core andrealize that it accomplishes the objects of the invention. While theinvention has been described in detailwith respect to its use as thecore of an automobile radiator, it will be readily understood that as aheat exchanger it is adapted to diverse other uses; and while referencehas been made to the circulation of liquid through tubes 13, and to thetransverse passage of air through' openings 16 and between the tubepanels, it will be readily understood that other coolant uids will,under various circumstances, be utilized instead of air or water, orboth.

While a complete disclosure of one embodiment of the invention has beengiven to illustrate the construction and operation of the same, it isnot to be understood that the invention is limited to the details of theforegoing disclosure. On the other hand, those skilled in the art willreadlv understand that the essential features of the present inventionmay be adapted and applied in other forms, and hence such adaptation andapplication as does not depart from the spirit of the invention iscontemplated by and within the scope of the appended claim.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

A heat exchange core comprising a metal sheet having a series of zig-zagfolds constituted of a plurality of tube panels in spaced substantiallyparallel relationship and panel interconnecting bends alternating withsaid panels, said panels each containing therewithin at least oneelongated hollow passageway extending parallel with said bends, themetal at the bends being perforated to permit uid passagewaytransversely across the exterior surfaces of the hollow passageways ofeach of said panels, and tins integral with the bends projecting betweensaid panels.

References Cited in the le of this patent UNITED STATES PATENTS 965,189Hyde et al July 26, 1910 1,528,461 Woolfe Mar. 3, 1925 1,542,905N'orrlin June 23, 1925 2,458,629 Orley Jan. 11, 1949 2,462,136 SmithFeb. 22, 1949 2,690,002 Grenell Sept. 28, 1954 FOREIGN PATENTS 290,868Great Britain May 24, 1928

